Thermal sensor and current generator

ABSTRACT

In a system to prevent train derailment due to axle failure resulting fromournal bearing overheating, a thermal sensor continuously monitors the temperature of the bearing and activates the brake system when the temperature exceeds a predetermined level. A thermally-responsive element located in the journal bearing housing physically deforms to activate a power source. The resulting signal initiates an electro-explosive brake line venting mechanism, which punctures and vents brake line to stop the train. Several configurations of the thermal sensor and the power source are possible.

This is a division of application Ser. No. 495,478, filed Aug. 7, 1974,and now U.S. Pat. No. 3,930,629.

BACKGROUND OF THE INVENTION

This invention relates generally to sensor systems and more particularlyto a thermal sensor system which detects incipient wheel journal bearingoverheating on rail vehicles and activates the air brakes to stop thevehicle prior to bearing failure and possible derailment.

Railroad journal bearing failures due to overheating resulting inaxle-end fracture and consequent dropping of the rail car sideframe tothe roadway have been a most prevalent source of major accidents. Thesefailures, called "hotboxes", if not detected in time, may lead toaccidents that result in losses of millions of dollars and risk thelives of persons aboard the train, or in the vicinity, particlarly wherehazardous cargoes are involved.

Present methods of detecting hotboxes include inspection in train yardsand from passing trains by railroad personnel. Along main lines, bearingtemperatures are monitored in route by automatic, track-side, infrareddetectors. Inspection by railroad personnel is, however, time-consumingand costly since each journal box has to be individually checked.Automatic wayside infrared detection stations have been installed atseveral hundred locations. These units, capable of scanning each bearingon a passing train and reporting and/or recording its temperature, havebeen developed to a point of excellent effectiveness. However, at a costof approximately $50,000 each, plus data transmission equipment toautomatic signals or manned monitoring points, they have not generallybeen installed on low-traffic-density lines or at close enough intervalson mainlines to detect all hotboxes before catastrophic failure candevelop.

Higher speeds, heavier loads, extended runs and other factors havenecessitated the increased use of more expensive roller bearings andimproved bearing lubrication systems to reduce bearing failures. Thereduction in bearing failures, however, has not brought about acorresponding decrease in hotbox-caused derailments because the rate ofderailments per detected hotbox has increased, resulting in a relativelyconstant hotbox derailment total. The decreased rate of detection may beattributed to several factors, such as the more rapid progression frominitiation of bearing failure to catastrophic assembly failurecharacteristic of roller bearings and the less detectable early signs ofroller bearing failure than bearings with lubricator pads.

Actual axle failure from a hotbox occurs from heating to a temperaturewhere the steel is significantly weakened, since nominal stress levelsare low. The energy input available from the maximum torque input fromone pair of wheels to a seized bearing assembly is sufficient to raisethe axle-end steel to 1000° F. in less than one minute. It is not likelythat this concentrated an input will occur in an actual assembly, but itis apparent that failure can occur in a matter of a very few miles orminutes of travel. Continuous, automatic monitoring of each bearing maybe expected to provide virtually 100% protection from this mode offailure, provided the thermal path to the sensor is as short as thatfrom the bearing to the axle and there is no significant time lag in thesensor.

Once a trouble signal is generated at one of the sensor locations, e.g.,at the journal housing, and amplified to a usable power level, economiclogic dictates that it be transmitted to a single, on-car location toactuate the inter-car communication link input. Several aspects of anysuch system are vital. Parallel inputs into the communication link mustbe mutually compatible. Failure of one or more sensors should not impairsystem operation. System refurbishment after an actuation, if requiredat all, must be reasonably inexpensive and capable of accomplishment atrelatively widespread and unsophisticated facilitites. Low cost over thecomplete life cycle, including all initial hardware costs, installationand check out, maintenance and repair, periodic continuity checks, andaccommodation to other car maintenance procedures is vital to system.Demonstrable ruggedness and predictable life are particularly importantto acceptance of a sensor system.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a new andimproved thermal sensor to monitor journal bearing temperature.

Another object of the invention is to provide a new and improved journalbearing temperature monitoring sensor that is efficient, reliable andautomatic in operation.

Another object of the invention is to provide a new and improved journalbearing temperature monitoring sensor that is easily and economicallyincorporated into existing train equipment.

Another object of the present invention is the provision of a new andimproved journal bearing thermal monitoring sensor that is rugged andquickly and inexpensively refurbished.

Yet another object of the present invention is the provision of a newand improved journal bearing temperature monitoring sensor that producesan output signal upon sensing a predetermined temperature.

A further object of the invention is the provision of a new and improvedjournal bearing temperature monitoring and actuation system capable ofactuating the train brake system to stop the train upon detecting apredetermined temperature.

Still a further object of the invention is the provision of a new andimproved journal bearing temperature monitoring and actuation systemcapable of automatically, reliably and efficiently actuating the trainbrake system to stop the train upon detecting a predeterminedtemperature, the monitoring and actuation system being rugged,economical and quickly refurbished.

Briefly, these and other objects of the present invention are attainedin a thermal monitoring sensor housed in a roller bearing adaptercomprising a quick-response, percussion-initiated electric generatoractivated by a heat-deformable temperature sensor. The electric signalis utilized to activate an electroexplosive brake line venting mechanismattached to the brake line. An explosively-driven bellows motor actuatoris triggered by the signal, causing a diaphragm cutter to rupture andvent the brake line, stopping the train prior to bearing overheating.

BRIEF DESCRIPTION OF THE DRAWINGS

Still other objects and many of the attendant advantages and features ofthis invention will be readily appreciated as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings wherein:

FIG. 1 is a partial, sectioned view of the sideframe showing the thermalsensor installation of the present invention;

FIGS. 2a, 2b and 2c are sectioned views of alternative embodiments ofthe thermal sensor;

FIG. 3 is a view along line 3--3 of FIG. 2b;

FIG. 4 is a partially-sectioned, plan view of a train car embodying theanti-derailment system of the present invention;

FIG. 5 is an elevation view of the train car of FIG. 4;

FIG. 6 is a partially-sectioned view of the brake line ventingmechanism; and

FIG. 7 shows the bellows motor actuator of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings wherein like reference charactersdesignate identical or corresponding parts throughout the several views,and more particularly to FIG. 1 thereof wherein the thermal monitorsubsystem of the anti-derailment system is shown to include the thermalsensor 10 schematically shown positioned within a recess provided in astandard roller bearing adapter 12 positioned in the sideframe 14.Connected to the sensor 10 is an electric current generator 16 which isactivated by the sensor, the current being carried to the brake actuatorsubsystem by means of a shielded conductor 18, such as sheathed orarmored cable.

FIGS. 2a, 2b and 2c illustrate alternative embodiments of the thermalsensor 10-current generator 16 combination. Sensor body 20, of suitablethermal-conductive material such as aluminum or steel, is provided withan axial bore 22 extending substantially the length of the body. Thelower, closed end of bore 22 provides a containment means for a spring24 which biases a hardened firing pin 26 upwardly against a thermalrelease pin 28 extending from a transverse bore approximately midlengthof body 20. The interior extremity of release pin 28 has a chamfer 30which contacts a chamfer on the end of the firing pin 26 to restrain thepin against spring 24.

The open end of bore 22 is provided with a number of concentriccounterbores to receive elements which comprise the assembled thermalsensor 10. Positioned in a first counterbore of a diameter larger thanbore 22 is a combined stab detonator and electric power source 32similar to those used in ordnance fuzing systems. The detonator/powersource 32 comprises a cup-shaped housing 34; a stab detonator 36positioned within the housing; a wave shaper 38 surrounding thedetonator to moderate the explosive force and to transmit the pressurewave to the piezoelectric element 40 abutting the wave shaper; andcontact terminals 42 abutting the power source and extending from thebody 20 for electrical connection. A disc 44, having an aperture toreceive contact 42 is pressed into a larger counterbore and suitablyfastened to secure the detonator/power source 32 in place. An insulatorsleeve 46 encircles contact 42 within the disc aperture. Encircling theinner end of contact 42 and positioned between the piezoelectric element40 and the disc 44 is a sleeve-like resistor element 48 to bleed off anystatic charges.

Thermal release pin 28 may be made from 55-Nitinol, the generic name fora series of nickel-titanium intermetallic compound alloy having a unique"memory" property developed in 1961 by the Naval Ordnance Laboratory.Nitinol alloys, an acronym of Nickel Titanium Naval Ordnance Laboratory,have chemical compositions in the range from about 53 to 57 weightpercent nickel and the balance titanium. The "memory" properties aresuch that, given the proper conditions, Nitinol objects can be restoredto their original shape even after being "permanently" deformed out ofthat shape. The return to the original shape is triggered by heating thealloy to a moderate temperature. Considerable force is exerted andmechanical work can be done by the material as it "snaps back" to itsoriginal shape.

Nitinol will undergo a martensitic (diffusionless) transition with theability of the alloy to undergo such a crystalline transition beingtemperature dependent. The maximum temperature at which this transitioncan occur is called the critical temperature and this temperature is afunction of the alloy composition. The martensitic transition may beproduced by deforming Nitinol below its critical temperature and thistransition, due to the structural change taking place in the molecules,is accompanied by the liberation of heat energy. Then, if Nitinol isheated in its deformed condition to above its critical temperature, itwill move in a direction opposite to the direction in which it has beendeformed, and during this movement the Nitinol is capable of producinguseful work.

The compositions and properties of Nitinol are described more fully inU.S. Pat. No. 3,174,851, issued Mar. 23, 1965. Briefly, the steps inimparting a shape "memory" to a Nitinol article include: forming thealloy into the shape that it will be called upon to "remember", i.e.,its "memory configuration"; heat treating the Nitinol shape while it isconstrained in a fixture and subsequently cooling it below thetransformation temperature range; and then straining the part to an"intermediate shape", which is the shape that the part is to retainuntil it is heated to restore it to the memory configuration. Thetemperature to which the part must be heated in order to return it tothe memory configuration depends upon the chemical composition of thealloy. This is described more fully in U.S. Pat. No. 3,558,369, issuedJan. 26, 1971.

As the 55-Nitinol part, in its intermediate shape, is heated to returnto its memory configuration, the alloy exerts a very considerable forceand can do significant mechanical work. Reference may be had to U.S.Pat. No. 3,403,238, issued Sep. 24, 1968, which discusses thisphenomenon more fully.

The thermal release pin 28, strained in tension below its thermaltransition temperature, restrains the spring-loaded firing pin 26. Atthe temperature range determined by its composition and processing,release pin 28 shrinks to its shorter, memory configuration and releasesfiring pin 26.

Instead of the thermal release pin 28 of FIG. 2a, the thermal sensorshown in FIG. 2b utilizes a low-melting-point alloy to release thefiring pin. Sensor body 20' is similar to body 20 of FIG. 2a, exceptthat the lower portion is of reduced diameter which is provided with anannular groove to receive a low-melting-temperature, eutectic alloy ring50 having a specific melting temperature, such as alloys ofbismuth-lead-tin, bismuth-cadmium-tin, or combinations thereof. Eutecticalloys, or those alloys melting completely at a specific temperature,are most suitable. As shown in FIG. 2b and in the cross-sectional viewof FIG. 3, firing pin 26' has a circumferential, V-shaped groove 52which receives a plurality of steel retaining balls 54 positioned inholes between bore 22 and the alloy ring-receiving annular groove.Firing pin 26' is restrained against the spring 24 by the balls 54 whichin turn are restrained by a segmented ball retainer 51. The alloy ring50 surrounds the ball retainer 51. A closure sleeve 56 encloses thereduced-diameter portion of sensor body 20', covering the ball retainerand the alloy ring. A gap or void 58 is provided between one side of thebody 20' and sleeve 56. When the sensor 10' experiences a temperatureexceeding the melting temperature of alloy ring 50, the ring melts andflows into the gap 58, freeing the retaining balls 54 to release thefiring pin 26'.

The operation of the thermal sensor is apparent from the foregoingdescription. Sensor 10 or 10' is heated by the overheated journalbearings, and with the sensor 10 of FIG. 2a, the increased temperaturecauses the thermal release pin 28 to shrink, as set forth above, and inthe sensor 10' of FIG. 2b, the alloy ring 50 melts. Spring-loaded firingpin 26 and 26' are then released to impact upon detonator/piezoelectricpower source 32, activating the detonator 36. The resulting explosiveforce, controlled by wave shaper 38, impinges upon the piezoelectricpower source 40 to produce an electrical output which is utilized by thebrake actuation subsystem of the present invention.

The electric power source may be of the piezoelectric element shown inFIGS. 2a and 2b or the thermal battery shown in FIG. 2c. Both of thesemeans are known to those skilled in the art. Piezoelectric materials,such as lead zirconate/lead titanate sintered elements, electricallypolarized to obtain the proper stress-output axis, are crushed by theexplosive force of detonator 36 to produce a relatively high voltage ofshort duration. In a typical low-resistance output circuit the currentis approximately 35 amperes. Since there is a "race" between generationof a large electrical output from the extremely high explosive-generatedpressures on the crystal and its termination by destruction of theelectrical continuity of the output, the aluminum "wave-shaper" 38 isused to strike a balance between these opposed events.

The sensor 10" of FIG. 2c is similar to that of FIG. 2a except that thepiezoelectric element has been replaced with a thermal pulse battery 60.A stab-type percussion primer 62 is activated by the firing pin 26 toproduce a flame which ignites layers of pyrotechnic material within thewaffer-type cells of the heat pads 64. Burning of this material producessufficient heat to melt the electrolyte, a salt such aslithium/potassium chloride, deposited within the electrochemical cells66 between the heat pads 64. Once the electrolyte is melted and its ionsreleased, normal electro-chemical action generates voltage until theactive materials are depleted or cooling resolidifies the electrolyte.Terminals 68 serve their customary purpose as electrical outputconnectors. A snap ring 70 secures the thermal battery 60 within thereceiving bore of the sensor body 20, and a resistor 72 joins theterminals 68 to facilitate electrical continuity check during testing ofthe system. In operation sensor 10" function similarly as sensor 10 ofFIG. 2a except that shrinking of the thermal release pin 28 permits thefiring pin 26 to ignite the pyrotechnic material in the thermal batteryto produce the electric current. Of course, thermal battery 64 may alsobe used with the sensor 10' of FIG. 2b.

FIGS. 4 and 5 show the plan view and elevation view, respectively, of atrain car 76 provided with the brake actuation subsystem of the presentinvention. Positioned in the sideframes of each train truck are thethermal sensor 10, 10' or 10" of FIGS. 2 which continuously monitors thetemperature of the journal bearings and activates the brake actuationsubsystem once the bearing temperature exceeds a predetermined limit.The thermal sensors 10, each with its associated electric power source16, are electrically connected by the shielded conductor system 18 tothe brake line venting mechanism 92. Shielding of the conductor preventsstray electromagnetic signal interference and protects against theadverse environment beneath the rail car truck. The train's brake line78 extend the length of car 76 and terminate in end couplings 80.Connected to the train line 78 are other components of the pneumaticbrake system common in train cars, including the brake valve 84, brakecylinder 86 and brake reservoirs 88.

Positioned on the brake pipe 90 joining the brake valve 84 to the trainline 78 is the brake line venting mechanism 92, shown more fully in FIG.6. The venting mechanism includes an electromagnetic radiation shield 94surrounding a diaphragm cutter having a cylindrical housing 96; anexplosively-driven bellows motor actuator 98 connected to the electricalconductors 18 positioned at one end of housing 96; a slidably-mountedcutter 100 disposed adjacent the actuator 98; a shearable diaphragm 102positioned adjacent the other end of housing 96 to separate the housingfrom the internal passage of brake pipe 90; an annular passage 10;provided in the housing 96 to permit passage of air from the brake pipe90 after diaphragm rupture; and a calibrated venting orifice structure104 to vent the released air. Also visible in FIG. 6 is the dirt chamber106 and the cut-out cock 108, elements common to train brake systems.The shield 94 around the diaphragm cutter serves the same purpose as theshielding around conductor 18. The diaphragm cutter may be similar tothat disclosed in copending application Ser. No. 465,400, filed Apr. 29,1974and now abandoned, and the explosive piston-type cutter actuatordescribed therein may be used in place of the bellows motor actuator 98.

Details of the bridge-wire bellows motor actuator 98 may be seen in FIG.7 wherein the wires 110 of the shielded conductor 18 are positionedagainst a propellant 112 contained in cup 114, the ends of wires 110being joined by a fine bridge wire 116 embedded in the propellant wires110 are suitably insulated with insulating material 118, and cup 114 issealed with a plug 120 of glass, plastic or other suitable material.Bellows 122 is pleated from suitable malleable, ductile metal, such ascopper, with the forward end formed into a blunt nose 124 and the edgeof the aft, open end crimped over the seal plug 120. Approximate thisopen edge, the bellows 122 is provided with an outwardly-extending ridge126, which receives a similarly-shaped ridge formed on the propellantcup 114 to properly position the cup.

The operation of the bellows motor actuator 98 and the venting mechanism92 can be readily seen from the foregoing description. Briefly, thepropellant 112 is ignited by the signal generated by current generator16, as set forth above, the expanding gases forcibly extending thebellows 122, causing the blunt nose 124 to contact and displace cutter100, which in turn severs diaphragm 102 to release the air from brakepipe 90, thus slowing and eventually stopping the train. The escapingair flows out through passage 103 and the venting orifice 104. As theair flows through orifice 104, a distinct, audible sound is produced tohelp the train crew locate the car which has been braked and to correctthe possible derailment-causing condition. This permits remedial actionprior to any actual derailment. Additionally, the actuation of the brakesystem can be monitored from a central location, such as the engine cab.

Bellows 122 is sufficiently rigid after expansion to prevent cutter 100from being forced by air pressure back through the ruptured diaphragmand possibly obstructing the flow. To further assure free air flow,cutter 100 may be hollow with an opening 128 therein to permitunobstructed flow between the brake pipe 90 and annular passage 103.

Obviously, numerous modifications and variations of the presentinvention are possible in the light of the above teachings. It istherefore to be understood that within the scope of the appended claimsthe invention may be practiced otherwise then as specifically describedherein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. A thermal sensor for producing an output signalat a predetermined temperature comprisinga deformable,temperature-responsive means formed out of an alloy having memorycharacteristics; a spring-biased firing pin releasably restrained in acocked position by said temperature-responsive means and spaced from adetonation means; and a current generator means responsive to the impactof said firing pin and said detonator means to produce an output currentupon release of said firing pin by said temperature-responsive means ata preselected temperature.
 2. The thermal sensor of claim 1 wherein saiddeformable, temperature-responsive means comprises a material whichundergoes a phase change at a predetermined temperature.
 3. The thermalsensor of claim 2 wherein said temperature-responsive material comprisesan eutectic alloy having a predetermined melting temperature.
 4. Thethermal sensor of claim 3 wherein said alloy comprises an alloy ofbismuth.
 5. The thermal sensor of claim 3 wherein said current generatormeans comprises a piezoelectric element initiated by impact of saidfiring pin.
 6. The thermal sensor of claim 5 wherein said piezoelectricelement comprises a detonator initiated by impact with said firing pinand piezoelectric crystals crushed by pressure from said detonator toproduce an electric current.
 7. The thermal sensor of claim 3 whereinsaid current generator comprises a thermal battery activated by impactof said firing pin.
 8. The thermal sensor of claim 7 wherein saidthermal battery comprises:a pyrotechnic reactant; an electrochemicalreactant; and a percussion primer triggered by impact of said firing pinto initiate an electric-current-producing reaction between saidpyrotechnic reactant and said electrochemical reactants.
 9. The thermalsensor of claim 2 wherein said deformable, temperature-responsivematerial comprises an alloy having a crystalline phase change at apredetermined temperature.
 10. The thermal sensor of claim 9 whereinsaid crystalline phase change alloy comprises an intermetallic alloy ofnickel and titanium having a shape change above a predeterminedtemperature.
 11. The thermal sensor of claim 10 wherein said currentgenerator prises a piezoelectric element initiated by impact of saidfiring pin.
 12. The thermal sensor of claim 11 wherein saidpiezoelectric element comprises a detonator initiated by said firing pinand piezoelectric crystals crushed by pressure from said detonator toproduce an electric current.
 13. The thermal sensor of claim 10 whereinsaid current generator comprises a thermal battery activated by impactof said firing pin.
 14. The thermal sensor of claim 13 wherein saidthermal battery comprises:a pyrotechnic reactant; an electrochemicalreactant; and a percussion primer triggered by impact of said firing pinto initiate an electric-current-producing reaction between saidpyrotechnic reactant and said electrochemical reactants.